Control apparatus for air-operated devices



Jan. 26, 1960 w, F, p w ows 2,922,594

CONTROL APPARATUS FOR AIR-OPERATED DEVICES Filed March 25, 1957 1N VEN TOR. WALTER F PAWLOWSKI BYMK% ATTORNEY United States Patent CONTROL APPARATUS FOR AIR-OPERATED DEVICES Walter F. Pawlowski, Holbrook, Mass.

Application March 25, 1957, Serial No. 648,390

2 Claims. (Cl. 24275.53)

This invention relates to control apparatus and reference is made herein to my copending application Serial No. 582,193, filed May 2, 1956. This invention represents a modification of the structure of the automatic control means as described in said application. 7

The principal object of the present invention resides in the provision of means providing an air control, as for instance for an air clutch which is adapted to be driven by a motor to drive a winding or reeling roll or pump, or any other device, and including means' providing a pneumatic impulse signal to apply a variation of air pressure to the clutch, said means comprising a device which is movable according to the variation of a load imposed thereon and directly controlling the action of an air relay valve for opening and closing or varying the opening thereof, whereby an automatic signal from the source of air pressure going directly to the clutch is variably applied so as to increase or decrease the torque applied to the driven device by means of the clutch; and the provisionofa control device as above described including a novel valve arrangement for the purpose of introducing a manual control of the clutch as well as an automatic control, it merely being necessary to selectively change the opernation of the device between manual control position and automatic control position as described above; and the provision of means bleeding the air supply pressure providing that under manual operation the system is stabilized at a fixed value for each different setting of a needle valve restriction inserted in the air circuit.

Other objects and advantages of the invention will appear hereinafter.

Rerference is to be had to the accompanying drawings, in which:

Fig. 1 is a diagrammatic representation of an entire control system and illustrating the same in condition for manual operation thereof; and

Fig. 2 is a view illustrating the valve in condition for automatic operation.

This invention has been illustrated as applied to a winding and reeling apparatus, and the novel control system is particularly adapted for textile operations. However, the invention is not limited to such an adaptation and may be used particularly in any relationship wherein the speeds are of a relatively low order but wherein it is desired to provide an automatic control of a high order of sensitivity and action.

There is illustrated at 10 a stand for reeling or unreeling a web 12 and another stand is illustrated at 14, the roll 14 being driven as for instance by a shaft 16 by means of a variable pneumatic clutch 18 of commerical design, in turn driven by a motor 20. Aline, as for instance at 22, applies air to the clutch in order to control the torque being applied. Although a clutch is here referred to, any other air-operated control device may be used.

The web 12 proceeds over a load-sensing roll 24 which is mounted on a block 26, the block in turn being mounted upon an element 28 which may be referred to as the force lever. This element is maintained on an air cushion, as for instance in the cylinder 30 by means of an air supply 32. If the air supply 32 is maintained constant, as for instance by an adjusting regulating valve at 34, when the load rises and falls the element 28 will rise and fall in proportion therewith and will operate a valve element 36 in the air relay valve 38 0 against the action of a spring 40 therein in order to variably open and close a valve diagrammatically shown at 42. The air-relay valve 38 is vented at 39.

Any source of air may be applied through the conduit at 44 and filter 45 for supplying the entire system, and a conduit 46 supplies the 'valve 36, and therefore it will be seen that the air pressure in the conduit 48 leading from the valve will vary according to the load imposed upon the roller or load-sensing signal device 24.

A needle valve 50 is inserted in the conduit 48 which leads to a novel valve generally indicated at 60. As shown in Fig. 1, the valve 60 is closed with respect to the conduit 48, so that automatic operation of the loadsensing device, above described, is out of operation.

Instead, a conduit 54 is provided leading from the air supply. This conduit is provided with an adjustable needle valve 56 leading to a port 58 in the valve 60. This valve has ports 58, 62, 64, 66 and 68. In the manual position of the device illustrated in Fig. l, the air supply passes through the needle valve 56 into port 58 and out the port 62 whence it passes by a venting device 70 and re-enters at port 64, passing to port 66 and thence out through a conduit 72 to conduit 22 to the clutch or other air-operated device 18.

However, if the valve 60 be turned to the position shown in Fig. 2, the automatic signal enters a passage 74 and out through the port 66 to conduit 72 and thence to the clutch 18, as before, and thus it is seen that a simple repositioning of the valve provides for a fixed manual operation of the device or for the automatic operation of the device, and when in the automatic position, ports 58, 62 and 64 are each selectively blocked such that there is no wasteful loss of air from the system to atmosphere. The passage 74 is out-of-line of port 58, and is closed in Fig. 1.

In the automatic operation of the device, the variation of pressure on the clutch is obtained simply through the source of air 4.4 passing through the valve 38, and is controlled thereby; but under manual operation, the valve 56 may be manipulated to provide for changes in torque if such is desired.

In manual control position, adjustment of the needle valve restriction 56 permits the feeding of any required pressure signal to the clutch, and this value can be read on the output gauge 76. If adjusted for the desired web tension while the machine is operating, automatic control may be obtained in two succeeding steps. In the first place, adjustment of pressure in conduit 32 is made by loading the piston in the cylinder 30 to locate a point of balance with respect to the load pres,- sure on the piston. At the balance point, the air relay valve at 38 will change position and this is indicated by an air pressure change at the control point indicator gauge 78. When this condition is obtained, changing the valve 60 from manual and to automatic places the control on the automatic control.

This invention permits the operator to record the manual output pressure for certain conditions on winding or unwinding operation and the control points for the particular material being processed so as to duplicate conditions at other times when running identical goods. When an operation is completed, manipulation of the control valve 60 to manual position will immediately restore correct output pressure to the clutch for the next roll of goods, etc. As soon-as the next roll of goods has been placedin motion, valve. 60 may then be turned toautomatic. position. This reduces operative actuation and progresses to arsimple. two-step manipulation of the valve 6.9 for. each roll of goods processed.

Control action is. initiated as a function of avariable deviatingfrom a fixed value which it is desiredv be maintained... The variable is indicated as a force and is balanced by an opposing force which is independently controlled at a. regulated value. Thus the control point is a fixed standard of comparison. As the variable measurement deviates about the desired control point, a signal device illustrated. as the air valve 38 is actuated by a direct mechanical connection. The signal from this device thus travels between two values, zero or maximum'as the variable load deviates above or below the. required value. Since the remainder-of the automatic control circuit functions from this basic concept of balancing of a variable measurement against a fixed standard force, the primary feature gained thereby is the fact that over-all accuracy of the system is not a percentage function of any span of operation, but merely the mechanical error introduced by resistance to movement of members incorporated in the design of the load-sensing-signal-device assembly combination. Thus, regardless of minimum or maximum value or setting of the control point, accuracy is a constantfactor and thus error is minute, particularly at the upper limits of operation.

The second feature ofv this control mechanism is a result of the adjustable resistance introduced in the line from the air relay valve. This restriction modulates the air signal which is initiated as a direct result of deviations of the controlled variable from the desired standard of comparison or control point. A correcting signal is thus fed as an output directly to the final control element of the control loop. The extreme sensitivity of the load-sensing device leads to an extremely.

high order of control accuracy.

It is to be understood that the present invention may have many diiferentapplications but it is particularly adaptable to relatively slow speed operations. The clutch 13 may be utilized as a brake if desired and many other changes in the invention in specific applications may be made without departing from the scope of the invention.

Having thus described my invention and the advantages thereof, I do not wish to be limited to the details herein disclosed, otherwise than as set'forth in the claims, but what I claim is:

1. Automatic control mechanism comprising a source of air under pressure, a load detecting device, means to pre-set the latter including an air cylinder and a regulator valve therefor, an air relay valve, an air-operated device actuated by the source of air pressure, the air relay valve being located in the airline between the air pressure source and the device, means in the relay valve for varying the air pressure passed thereby, means associated with the load detecting device to actuate the second named means according tothe load impressed on the air cylinder of the load detecting device, means to transfer the air pressure directly'to the air operated device -by-passing the air relay valve, and manually-operated means to control the airpressure in the air transfer means.

2. The control mechanism of claim 1 including a metering means comprising a needle valve located in the line between the air relay valve and theair-operated device.

References Cited in the file of this patent UNITED STATES PATENTS 1,529,218 Sandwell Mar. 10, 1925 2,164,599 Tyler July 4, 1939 2,422,758 Temple June 24, 1947 2,469,004 Rosebrough May 3, 1949 2,521,413 Scheuermann et a1. Sept. 5, 1950 

